Dimmer compensating circuit



April 19, 1960 A. 1 BAsTlAN DIMMER COMPENSATING CIRCUIT 2 Sheets-SheetZ Ii M. M.

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QN QQ Filed Jan. 23, 1956 DIR/[MER COMPENSATING CIRCUIT` Arthur L. Bastian, Yonkers, N.Y., assignor to Ward Leonard Electric Co., Mount Vernon, N.Y.,Ya corpo` ration of New York Application January 23, 1956,. Serial No. 560,525

Claims. (Cl. S15-i206) The invention relates to variable output voltage circuits and apparatus and is directly particularly tothe supplying of an output voltage over a ranger in a given predetermined relationship with a range of input control voltages irrespective of the value of output current at each voltage.

In electrical apparatus providing an output voltage the output voltage varies with the output current provided by the apparatus. It is often desirable to vary the output voltage over a range of values in response to a range of input control voltages with each output voltage corresponding to an input voltage and at each voltage to provide a range of currents depending on the load. The purpose of this invention is to provide compensating means to maintain each output voltage constant over the range of current so that each output voltage will correspond to a particular input voltage irrespective of the amount of current supplied at that particular output voltage.

This invention is particularly applicable to the remote` control of a plurality of incandescent lamps. In the remote control of groups or banks of lamps the operating characteristics of the control apparatus change with loads of different Wattage ratings. A given setting of the apparatus will produce different degrees of illumination of a single element depending on the total wattage of all elements. It is preferable that a given setting of the input control will cause the same outputr voltage to be impressed across each load unit irrespective of. the number of` elements so loaded.

An objectr of the invention is to provide an electrical apparatus for delivering a range of currents at each outputvoltage of a range of output voltages with the particular output voltage remaining 'constant over the range of currents.

Another object of the invention is to provide an electricall apparatus having a range of output voltages corresponding to a range of input control voltages irrespective of the current provided at each output voltage.

A further object of the invention is to provide an electrical apparatus for supplying a range of output voltages to a load in accordance with a range of input control voltages independent of 'the wattage of the load.

A stillfurther object of the invention is to provide lamp illumination control apparatus in which the intensity of illumination of each lamp of a plurality of lamps corresponds with a given value of input control irrespective ot the number or total number of lamps connected to the output of the apparatus.

Other and further objects of the invention will be apparenty from the following detailed description taken in connection with the drawings in which:

Fig. 1 is a block diagram of the main components of the apparatus;

Fig. 2 is a diagrammatic view of the circuit in accordance with the block diagram of Fig. l;

Fig. 3 is a schematic diagram of the divider circuit apparatus; and

ice

Fig. 4 is a schematicV diagramV of another embodiment of the divider circuit apparatus.

In this embodiment the load lil may comprise one or more incandescent lamps of high wattage. The lamps may be used for lighting stages or other types of areas requiring a high degree of illumination that may be varied over a wide range. The purpose of this appartus is to control this high wattage load by means of a small, low wattage control 11 such as a rheostat in the order of two Watts. The magnetic amplifier stages 12 and 13 may have,

ak capacity from 5-40 kilowatts depending upon the power requirements of the particular installation. of` stage 13 is connected to the load I0 by line 19. The amplifier stage 12 controls theI output of the second stage 13 and is in turn controlled by the control device 11. The control device 11 is adjusted through a range of voltages. Each voltage corresponds to a particular degree of illumination of each lamp of the load. This voltage is constant at each setting. The number of lamps or the total wattage of the load may be changed and the total load current for a particular setting may change but the illumination of each individual lamp will remain the same. In order to maintain the output voltage of stage 13 constant at a particular input Voltage, a cor rective signal is impressed on stage 12 which is proportional to the quotient resulting from the division of a signal proportional to voltage and a signal responsive to load current. This corrective signaly is created by a divider type circuit or unit 20. The divider unit comprises a multiplication apparatus 14 and a subtractingy and amn plifying circuit 15.`

The effect of the circuits 14 and `15 is to provide a signal approximately proportional to the division of the load voltage signal and the load current responsive signal. This quotient is fed back by line 16 to the stage 12 so that as the voltage drops, the ampliiication of stage 12 is increased. This increases the output voltage of stage 13 which compensates for the decrease in voltage, and thus the output voltage is maintained constant.

In Fig. 2 a detailed schematic diagram is shown of the dimming system. The stage 12 comprises a magnetic amplifier having two saturable reactors' 22 and 23 with anode windings 22a and 23a connected to the power lines 24a and 24b with rectitiers 25 and 26 connected in series with a respective winding and an output rectifier 27 for providing a D.C. output current.

The bias windings 22h and 2311 are provided with a direct current from the bias circuit 28 which is connected to a suitable direct current supply (not indicated) by lines 28a, 28h. The resistor 29 is connected across the lines 28a, 28h andV has an adjustable contact 29a for setting the bias current in accordance with the magnetic amplifier characteristics desired. A resistor 3i! is provided in series with the bias windings to limit the current to the windings to a predetermined maximum value.

The windings 22jc and 23f are connected in series to the output of the feedback circuit 31 connected to the load. The feedback circuit 31 is connected to the rheostat 34 to provide a feedback signal of the proper value. The circuit 31 rectiesthe alternating current by means of the full wave bridge rectier 39 and provides a lead network for anti-hunt and filtering purposes by means of the elements 53 and resistor54. The windings 22e and 23e are connected in series to the low wattage control 11. The control 11 comprises a potentiometerV 32 connected across a low-voltage, direct-current supply in the order of 6 to 12 volts. The amount of voltage impressed across the windings 22C and 23e is detern mined by the adjustable contact 32a. This contact determines the degree of intensity of illumination of the lamps in the load 10. The higher the voltage across the windings 22C and 23e, the greater the degree of illumina- The output tion will be made by the lampslll. A resistor 33 is connected in series with the control windings 22e and 23e. The D C. voltage impressed across the potentiometer 32 should preferably be very steady so that the lamps will not change in illumination at a given setting of the contact 32a.

The windings 221' and 2.3i' are connected inseries across the output of the divider circuit and particularly connected to the subtraction and amplication circuit 15. Pthe output of the divider circuit corrects the amplification characteristics of stage 12 to compensate for the variations in the characteristics of stage 13 with different Values of load. Thus, with a steady D.C. voltage impressed across potentiometer 32 and the correction provided by the windings 22:A and 23;', the illumination of each lamp of the load 1t) will correspond with a definite setting of the contact 32a, irrespective of the number of lamps in the load and the current drain on the stage 13.

The alternating output of stage 12 is converted by the rectifier 27 to a direct current and smoothed out by the iilter 35. The filter 35 comprises a choke 36, a condenser 37 and a resistor 38 in series with the choke. The stage 13 comprises a magnetic amplifier having saturable reactors 46 and 4l, each comprising a threelegged core. The output of filter 35 is connected across the control windings 4dr: and 41C of the reactors 40 and 41 respectively to impress thereon a direct control current for adjusting the output of the stage 13. The reactors are biased by the direct current supplied by the rectifier 79 connected to the supply lines. The anode windings 40a and 41a are connected in parallel between the A.C. power lines 24a and 24b, and have rectifiers 42 and 43 connected in series with the windings 40a and 41a respectively to pass direct current through each winding and provide an alternating current output from the stage 13. Connected in parallel across the rectifiers 42 and 43 are resistors 44 and 45 respectively. The input lines 46a and 46h are connected across the resistors 44 and 45 in series and carry a current to the filter network 47 which comprises a rectilier 48, a choke 49 and a variable resistor 50, all connected in a series. A condenser 51 is connected across the output thereof. The direct current output across the terminals 52a and 52b of the filter 47 provides a direct current that varies so that as the load current increases the direct current signal increases with the output load current of the power stage 13. The lines 20a and Ztlb are connected to the respective terminals 52a and 52b and impress the current on the subtraction circuit 15.

The variable reactor 55 may be connected in parallel or across the load 1li and has a contact 55a to tap a voltage therefrom proportional to the voltage across the load. The contact 55o is connected to the multiplying circuit 14, to impress thereon a current proportional to the load volt- The circuit 14 comprises a saturable reactor 56 which has athree-legged core with the anode windings 55a and 55a', wound on the outer legs and a control winding de wound on the inner leg. The voltage that is impressed across the control windings 22r and 23r of stage 12 is impressed across the control winding 56e and the current therein determines the degree of saturation of the reactor 56. Thus, an alternating current is passed through the windings 56a and 55a' proportionally to the load voltage.

A rectitier 57 is connected between the contact 55a and the anode winding 56a' to provide to the circuit 15 a direct current proportionally to the load voltage.

The circuit comprises two saturable reactors 60 and 61 with the windings tina, 60C and title', wound on the central leg of one reactor and windings 61a, 61a and 51e wound on the central leg of the other reactor. The control windings 66C and 61C are connected in series to the lines 21a and 2lb to receive a direct current proportional to the load current supplied to the load 10,

t 4 and windings 60e and 61e are connected in series to the lines 57a and 57b to receive a direct current therefrom.

The anode windings 60a and 61a are connected in parallel to alternately receive current from the power lines 24a and 24h. Rectifiers 62 and 63 are connected in series with a respective winding to alternately pass direct current through the anode windings 66a to 61a. Resistors 64 and 65 are in parallel with a respective rectifier. Thus the reactors 66 and 61 operate as a magnetic amplier. The output is connected to the rectifier 68 to rectify the output of the circuit 15 and provide a direct current over lines 17a, 17'0 to control winding 56C of the multiplying circuit 14 and over lines 16a, 16h to windings 22r and 23r of the stage 12.

In combining the signals in the multiplication circuit 14 and the subtraction and amplification circuit 15, it is of course understood that it is the fluxes produced by the currents of the signals passing through the respective windings that are being combined. These tiuxes are determined by the turns of the windings and the amount of current passing through the windings. The electrical units used in the computations are ampere turns or liux densities and not the currents and the voltages of the signals impressed on the respective windings.

he operation o'f the divider circuit will be discussed in detail in connection with Fig. 3 of the drawings. The reference numerals in Fig. 3 identify the corresponding elements shown in Fig. 2. A voltage A proportional to the load voltage is impressed across lines 18a and 18b to the divider circuit to pass an alternating current propo'rtiorlal to the load voltage through the lines and windings Srz and 55a to create a iiuX in the core 56h. The voltage E responsive to load current is impressed across lines 21a and 2lb to the divider circuit to pass a current through the central winding 6de' and 61e' to create a iiux in the respective cores. The output lines 16a and 16b of the divider circuit have a direct voltage C im pressed thereacross which is proportional to the division of the voltage B by the voltage A. This voltage C is also impressed across the control windings 56C to create another ilux in the core Sb. The fluxes are combined so that the output of the saturable reacto'r 56 of circuit 14 is equal to the product of voltage A and C which is an intermediate voltage D. The voltage D is impressed by lines 57a and 57h across the control windings 60e and 61C to create another linx in the respective cores. As previously stated, the voltage B impresses a current over lines 21a and 2lb through the series windings 60e' and 61e'. The windings 60e and 60C and 61C and 61C are wound on their respective cores so that the fluxes created in windings 6de and 61C' are subtractive from the fluxes created by the windings 60e and 61e respectively. The difference of these two fiuxes is amplitied by the reactors 5@ and 61 and the output thereof is impressed across the lines 16a and 16b as voltage C. Thus by multiplying the rectified output signal of circuit 15 by the voltage A and then subtracting the product from the voltage B and amplifying this difference, the voltage C is obtained which is proportional to the quotient resulting from the division of voltage B by the voltage A. This quotient provides a voltage which is responsive to the variations of load voltage and current for different values of load that corrects the characteristics of the stage 13.

When the winding 40a is supplying the main current to' the load 10, the current passes through the rectifier 42 to the load. Lines 46a and 46h are connected across the network of rectitiers 42, 43 and resistors 44, 45 to obtain a signal current to be supplied to the windings 60C' and 61e'. A path is provided for the current through the tilter 47 to the terminal 52h through line 2lb to the winding 61e' and thence to the winding 66e in series therewith to the line 21a to' the terminal 52a to the resistor 50 and the choke 49 of the filter 47, and then through the rectifier 4S to the line 46h. The main current supplied to the incandescent load does not increase proportionally with increase in load voltage'z At"y the: low voltages', the current increases 'at a` high' rate and at the higher voltages the increase is substantially' reduced. A dry disc selenium-type rectifier' has a` general opposite variation with respect to current and voltage; At low' voltage vary essentially linearly.` Thus', the corrective" signalproduced by the divider' circuit varies essentially linearly' with the main voltage and' produces a' linear c"orrect'ion.` o y IIf a lojad 10 isq supplied with current frein' stage I3 in wh'clr the inain current varies linearly with the fnan` voltage' tllenv the lines 46a4 and 46e may be connected across a resistor in the connecting lines to theload or' connected in any suitable fashion which would provid'e a voltage that would vary with the current; ItA is?- thus seen' that various types of circuits may be usedwith cor rective factors to compensate for non-linear variations between main current and main voltage. Alsothe divider circuit could be arranged to produce a corrective signal that does not vary linear-ly with the main voltage where it wouldl be desirable t'ohave arcorrective relationship between the divider circuitand the main voltage that is non-linear; This invention is not intended to be limited to any specific form of the divider circuit, but is readily adaptable to'various types of desired embodiments.

l A substantially co'ntinuous direct current is supplied to the/control windings 60e and 61c and 60e and 61a. The circuit 47 smooths the current supplied" to windings 60C and 61C' and a circuit 80, shown in Fig. 4, may be connected between the rectifier 57 and the windings 70e` and 71e. Thus, a substantially continuous flux is supplied to the reactors 60 and 61 to control the current passing through the anode windings. A substantially continuous current is supplied from the rectifier 68 to' the control winding 56e to continuously supply a control flux to the reactor 56. The system remains at equilibrium and responds quickly to changes in the value of the output voltage and output current. The change in the system is initiated by the change in the output current or output voltage. These changes are reflected in the various windings.

Fig. 4 is a modification of the circuit illustrated in Fig. i

3 and described hereinbefore.

In Fig. 3 the saturable reactors 60 and 61 each have two control windings 60C, 60e', and 61C, 61e. The modified saturable reactors 70 and 71 of Fig. 4 each have a single control winding 70c and 71c, respectively. The control windings 70C and 71c are connected in series across a full wave bridge rectifier 73 which is connected across the terminals 52a, 52b. The current signal which varies with load current is rectified by the rectifier 73 and the direct current smoothed out bythe filter 74 comprising resistors 75, 76 and condenser 77. A rectifier 78 is connected across the output of the filter to by-pass current. The direct current passes through the windings 70:, 71e. The direct current from the rectifier 57 in series with the multiplier windings 14 passes through the windings 70e and 71c in the opposite direction to the current from the rectifier 73. The currents flow in oppo'site directions in relation to one another so that the current in Vthe windings 70e, 71c is the difference of those two currents or the difference between the current relating to the load current and the product of the current proportional to the load voltage and the amplified difference. The magnetic amplifier multiplies this difference by ahigh amplification factor. The multiplied difference is rec- 6 tilted lsy'tlie rectifier 6s and' supplied to the windings 22e', 23a` over" lines 162i', 1Gb and tothe control winding-56e; As' indicated hereinbefore the divider circuit' may be utilized in the control of the output of'various types of electricalpower type apparatus and is not limited to The circuit may be modified and` adapted' to different types of apparatuswithout departing from the invention as set forth in the the illumination control circuits.

tifier, ai first't saturable. reactor having a' first ferromagnetic col-'e with a first control winding coupled to said rectifier" to receive an inverse' current from the rectifier, a second control winding creating a flux' in said core opposing saidV first ,contro-ll winding flux to produce a resultant difierentiaiA flux in said core and a main winding for passing a signal responsive to the differential flux, a second saturable reactor having a second ferromagnetic core with a second main winding coupled to the output of said power amplifier to receive a voltage signal proportional to the output voltage, said second saturable reactor having a third control winding for controlling the current through said winding, rectifier means connecting said first main winding, with said third control` winding to passa currentprcportional to the signal of said first main winding, second'Y rectifier means in series with said second main windi-ng,saidl second rectifier means coupled to' said secondI controlv means to provide said second control means with an intermediate direct current signal responsive to the product ofl the current proportional to the signal of the first main winding and the voltage signal to subtractively combine the fluxes of said signals to produce an amplified differential signal proportional to the quotient of the output current and voltage of said power amplifier, and means for connecting the output of said second rectifier means to said power amplifier to vary the characteristics of said amplifier so that each output voltage of the amplifier corresponds to a particular setting of the input control irrespective of the output current supplied to the incandescent illuminating means.

2. An electrical systerncomprising means for supplying output voltage and current to a load, means for producing a first signal linearly responsive to changes in the output voltage, means for producing a second signal linearly responsive to changes in output current, means for multiplying the first signal by a corrective signal to produce an intermediate signal and means for subtractively combining the second signal and the intermediate signal to produce a corrective signal proportional to the quotient of the output voltage and current, means for impressing said corrective signal on said means for multiplying the first signal and the corrective signal, and means for impressing said corrective signal on the supply to maintain a given output voltage constant with variations in output current.

i 3. A control apparatus for providing a corrective signal proportional to the quotient of a first and second input signals comprising a first electrical means having a firstk input and a corrective input and an intermediate output, said first electrical means factorially combining signals impressed on said first input and said corrective inputy to produce an intermediate signal proportional to the resultant of the factorially combined input signal and corrective signal, a second electrical means having an intermediate input and asecondinput and a corrective output, said second electrical means differentially combining the intermediate signal and the second input signal to produce an outputkcorrective signal proportional to the difference of the intermediate signal and the second input signal across said corrective output, means for connecting said intermediate output of said tirst electrical means to the intermediate input of said second electrical means and means for impressing a iirst input signal on said first input and a second input signal on said second input', to produce a corrective signal in the corrective output of said second electrical means proportional to the quotient of the first and second input signals on application of the irst and second input signals to said respective electrical means.

4. A divider type apparatus for producing an output signal proportional to the quotient of a irst input signal and a second input signal comprising a rst saturable reactor having a ferromagnetic core with a rst control winding for receiving a tirst input signal creating a controlling flux in said core, a second control winding for receiving an intermediate signal creating a flux in said core opposing the linx of said irst control winding and a first main winding for passing a current to produce a corrective signal; a second saturable reactor having a second ferromagnetic core with a second main winding for receiving a second input signal and having a third control winding for controlling the current through said second main winding, means for connecting said third control winding to said tirst control winding to pass a current proportional to the corrective signal Vof said first'l main winding; rectifier means in series with said second main winding; said rectifier means coupled to said second control Winding to provide an intermediate signal responsive to the product of tlie second input signal applied to the second main winding and the corrective signal passed by the tirst main winding to subtractively combine the uxes of the intermediate signal and the first input signal to make the corrective signal proportional to the quotient of the first and second input signals.

5. An apparatus for supplying electric current and voltage over a range in a predetermined relationship comf prising electric power means having an output supplying electric current and voltage over a range", a rst electrical means having a first input coupled to the output ofV of said electric power means for receiving a current signal,

and an output coupled to the corrective input of said first electrical means and coupled tothe electric power means; said second electrical means having means to subtractively combine the intermediate signal and the current signal to produce in the output of said second electrical means the corrective signal proportional to the quotient of the supply current and voltage arid apply to said corrective third input of said first electrical means and to said electric power means to vary the characteristics of said power means so that the supply voltage and current is varied over a range in a predetermined relationship.

References Cited in the file of this patent UNITED STATES PATENTS 2,001,567 Case May 14, 1935. 2,236,195 McKesson Mar. 25, 1941 2,319,378 Weisglass May 18, 1943 2,367,940 Gullikson Jan. 23, 1945 2,438,396 Jacobs Mar. 23, 1948 

